Gapital Gains Tax on a FHL

My house has an annex that I rent out under the FHL regime. The annex is a converted garage attached to the house: I would estimate it at about 10% or less of the total floor space. The house is the sole residence of me and my husband. We purchased the property in Nov 2019; the previous owners had also let out the annex but at the time omitted to tell us that it was subject to business rates. I understand that this means that should we dispose of the property in future we may be subject to capital gains tax. Please can you confirm: 1. Would sale of the house give rise to a capital gains tax liability? 2. How can the purchase and sale values be established? 3. Am I able to claim any capital allowances in respect of the purchase of the annex building (as distinct from its contents) to offset any future CGT liability? 4. If we cease the FHL business is it correct that we can apportion CGT libaility on a time basis eg lived here 10 years, operated FHL 5 years, liability is apportioned? But is the gain value established when the trade ceased or when the house is sold?

Hi,
We cannoot comment on future events as legislation may change. You can see current guidance here:
Capital Gains Tax: what you pay it on, rates and allowances
Thank you.

The house has already been purchased: 2 questions specifically relate to events that have already happened. I have read the guidance and cannot find answers. 2. How can the purchase [and sale] values be established? 3. Am I able to claim any capital allowances in respect of the purchase of the annex building (as distinct from its contents) to offset any future CGT liability? And if I were to sell tomorrow are you still unable to offer guidance as that relates to future events? A lazy and unhelpful response.

Hi,
We can only provide general information and guidance in this forum. For an answer to a detailed question of this nature, you would need to contact our Self Assessment team, or seek professional advice. 
Self Assessment: general enquiries
Thank you.